viruses part i - ksu facultyfac.ksu.edu.sa/sites/default/files/8-_viruses_i.pdf · adenovirus...
TRANSCRIPT
Viruses Part I
Viral Taxonomic Classification
• Order>> -virales
• Family>> - viridae
• Subfamily>> -virinae
• Genus>> -virus
• Species
• Order>> Picornavirales
• Family>> Picornaviridae
• Subfamily>> Picornavirinae
• Genus>> Enterovirus,
rhinovirus, hepatovirus
Adenovirus
Structure:
• Genome: double-stranded linear DNA virus.
• Capsid: Icosahedral (70 to 100 nm) is made up of 252 capsomeres (this capsid contain the double-stranded linear DNA).
• Non-enveloped viruse.
• Adenoviruses are large group of related viruses, have approximately 50 serotypes that can infect human.
Adenovirus
Adenovirus
Adenoviruses causes:
• Acute respiratory disease (usually).
• Pneumonia (occasionally).
• Acute follicular conjunctivitis, epidemic keratoconjunctivitis, cystitis, and gastroenteritis (occasionally).
• In infants, pharyngitis and pharyngeal-conjunctival fever are common
Properties of Adenovirus
• Stable in the environment.
• Relatively resistant to disinfection inactivated
by formaldehyde and chlorine.
• Stable in GI tract- can withstand low pH, bile
acids and proteolytic enzymes.
Adenovirus
Pathogenesis:
• Virus attachment to host cell receptor.
• Viral entry into the host cells.
• Viral un-coating, replication and assembly inside the cell nucleus.
• This productive cycle of virus kills the host cell as cellular DNA, RNA, and protein synthesis are all shut off during the course of infection.
• Infectious virus is released from dying host cells.
Adenovirus
Host Defense:
In adolescents and adults a high prevalence of
circulating neutralizing antibodies contributes
to widespread immunity against adenovirus
infections.
Cytotoxic T lymphocytes also recognize and
destroy adenovirus-infected cells.
Adenovirus Transmission
Acute Adenovirus Conjunctivitis
It cause follicular conjunctivitis can be seen as:
Pharyngoconjunctival Fever
Or
Epidemic Keratoconjunctivitis
Pharyngoconjunctival Fever
• Kids 5-15.
• Swimming pool conjunctivitis.
• Systemic signs, and lymphadenopathy is characteristic singe for the disease.
• Self limiting disease no treatment is needed, but topical antibiotics should be given to control secondary bacterial infection.
Epidemic Keratoconjunctivitis
• Young adults.
• No systemic manifestations
• Starts unilateral, then spread to other eye in a week or less
• Especially contagious, and often occurs in epidemic especially in crowded living conditions.
• Involves the corneal epithelium, and may be followed by corneal opacity lasting several years.
Prophylaxis
• Cleaning and sterilization of all instruments that touch the patient’s eye.
• Proper cleaning and chlorination of swimming pools.
• Frequent hand washing.
• General cleaning and good hygiene practice.
Diagnosis:
• Cell culture technique: growing of the virus in cell culture.
• ELIZA: detecting of virus antigen ELIZA.
• PCR.
Treatment:
• Broad-spectrum antitibiotics to prevent secondary infections.
• Topical corticosteroids can be given for patients with conjunctival pseudomembrane or photophobia.
Coxsackie viruses &
Enterovirus
Belong to family Picornaviridae
Characteristics of Picornaviridae Family:
• This family comprises five main genera: Enteroviruses (>70
subgroups including: Poliovirus, Enterovirus, Coxsackie viruses),
Rhinoviruses, Hepatoviruses (Hepatitis A), Cardioviruses and
Aphthoviruses.
• Genome: Single-stranded linear RNA.
• Capsid: Small icosahedral (22-30 nm)
• Non-enveloped
• Replicate in cytoplasm.
Picornaviridae family causes a wide range of illnesses.
Infection with various picornaviruses may be
asymptomatic or may cause clinical syndromes such as:
• Aseptic meningitis.
• Encephalitis.
• Common cold.
• Conjunctivitis.
• Mycarditis.
• Hepatitis.
• Poliomyelitis.
Transmission of Picornaviridae Family
• By ingestion of contaminated food or water.
• From person to person usually on unwashed hands that touched feces or surfaces contaminated with feces.
• Diaper-changing tables, and toys in day-care may transmit the virus.
• Inhalation of infectious aerosols.
• Cockroaches in sewage and flies that settle on excreta may act as transient vectors.
Acute Hemorrhagic Conjunctivitis
Etiology:
Enterovirus 70 & Coxsackie virus A 24.
Clinical Features:
Affects all age groups but mostly seen in young patients.
Contagious and transmission appears to be hand-to-eye.
Sudden onset.
Peak incidence: summer & fall
At first unilateral & quickly become Bilateral.
Watering, redness & painful swelling in the eyelids.
Conjunctivitis is more sever than adenovirus conjunctivitis and often accompanied by Sub-conjunctival haemorrages.
May cause transient blurring of vision.
Acute Hemorrhagic Conjunctivitis
Treatment:
• Only symptomatic treatment, it has a self-limiting course.
Usually lasts for 7 to 14 days.
• Broad spectrum antibiotics should be used to prevent
secondary bacterial infection and cross infection.
Assignment
Compare between viral conjunctivitis and
Bacterial conjunctivitis